This invention relates to an ophthalmic lens which is designed to minimize the amount of visible light reflected onto the retina from the edges of the lens. More specifically, it relates to an ophthalmic lens, especially an intraocular lens, which has a lens body with an edge surface designed to reflect incident light on the edge surface away from the retina.
Conventional intraocular lenses typically have flat edges that, under certain conditions, can reflect incident light onto the retina to produce unwanted optical images, such as halos, rings, or arcs (commonly referred to as "glare"). Typically, the images occur when the pupil dilates large enough to expose, or nearly expose, the edge surface of the lens. These conditions occur at night or in dim light. For example, the unwanted images can be produced while driving at night by light rays from headlights of oncoming cars as the rays reflect or scatter from the exposed edges of the lens.
The problem of glare has worsened for intraocular lenses which have been specifically designed for small incision surgery. Intraocular lenses for small incision surgery may have a lens body which is round or oval, but the diameter of the lens body is smaller than that of a lens designed for conventional surgery. Therefore, the edges of these small diameter lenses are more often exposed to incident light.
More commonly, intraocular lenses for small incision surgery have an oval shape. These oval shaped lenses are referred to as "ovoid" lenses, and such lenses are described in Clayman's patent, U.S. Pat. No. 4,298,994. Because of the method of manufacture of these ovoid lenses, the ovoid has thicker edges on the small diameter sides of the lens body. It is therefore particularly susceptible to reflections and glare, because the thicker edges provide more surface area for reflections and therefore amplify these problems.
The popularity of small incision surgery is increasing and the ovoid has become the lens of choice for many small incision surgeons. Edge glare is one of the main drawbacks of ovoid lenses. Popularity with these lenses will continue to grow if the glare problem can be controlled.
Unfortunately, lens designs which have attempted to deal with the glare problem have been far from practical or efficient in dealing with this problem. For example, U.S. Pat. No. 4,596,578 discloses an intraocular lens having a lens body and a deformable positioning member for fixing the position of the lens body in the anterior chamber of the eye. The lens body and the positioning member are separately inserted into the eye, and then connected together in the eye to form the lens. A portion of the positioning member covers the periphery of the lens body, and this portion may be shaped so that light rays contacting the periphery of the lens body are deflected away from the retina. While this lens design may work in theory to help minimize glare, it represents a cumbersome attempt to deal with this problem. It is clearly undesirable from a surgeon's point of view to have to first insert the lens body of the intraocular lens, and then afterwards insert a positioning member which must then be connected to the lens body.
Other attempts have been made to minimize the effect of glare in intraocular lenses. U.S. Pat. No. 4,781,717 discloses an intraocular lens having a lens body and an integrally attached rim surrounding the lens body which covers the edge of the lens body. Reduction in "edge effect" and glare can be achieved according to this patent by adding a different color or using a different material for the rim. U.S. Pat. No. 4,743,254 describes an intraocular lens having a lens body and a deformable glare attachment. The glare attachment and lens body form a circle, and the glare attachment can be envisioned as "flaps" which fold down so that the intraocular lens can be inserted through a small incision in the eye. The glare attachment is desirably opaque to reduce the transmission of light through this section in comparison to the optical lens body. Once again, while these two approaches may appear to work in theory to reduce glare, the lens designs are difficult to fabricate and create unnecessary complications for the surgeon when the lens is to be implanted into the eye. Additionally, these lens designs require incorporating a coloring agent or a different component into the lens composition, which further complicates the manufacturing process.
Another interesting design to minimize glare in an intraocular lens can be found in U.S. Pat. No. 4,755,182. This patent discloses an intraocular lens having positioning holes displayed on the periphery of the lens body to aid the surgeon in manipulating and inserting the intraocular lens into the eye. The positioning holes are drilled only partially through the lens body, and the interior surface of the hole is not polished. These design features for the positioning holes reduce glare significantly. However, there is no discussion relating to any means for reducing glare caused by incident light contacting the edge surface of the lens body of the intraocular lens.
While the discussion here has been limited primarily to intraocular lenses, the problem of edge glare is also inherent for other ophthalmic lenses. Although there is a major effort to design smaller intraocular lenses for small incision surgery, which has led to burgeoning edge glare problems, the reader should not overlook the fact that these problems also occur with other ophthalmic lens designs, particularly lens designs for contact lenses and spectacles.
In view of the pervasive nature of this edge glare problem for all types of ophthalmic lenses, it would be highly desirable to form an ophthalmic lens which is simple in design, and yet alleviates the problem of edge glare. More specifically, the ophthalmic community needs a lens with a simple one-piece design for the lens body of the lens which has an edge surface characterized in such a way that it significantly reduces or essentially eliminates the creation of unwanted glare.